This invention relates to the preparation of nonionic alkanol alkoxylates as the reaction products of alkylene oxides with detergent-range, i.e., C.sub.8 to C.sub.20, alkanols. More particularly, this invention is directed to an improvement in the process for the preparation of such surfactant materials which utilizes an alkoxylation catalyst which combines one or more aluminum compounds with one or more sulfur-containing acids.
Products useful, for instance, as nonionic surfactants, wetting and emulsifying agents, solvents, and chemical intermediates, are prepared by the addition reaction (alkoxylation reaction) of alkylene oxides with detergent-range alkanols. An illustration of the preparation of an alkanol ethoxylate (represented by formula III below) by addition of a number (n) of ethylene oxide molecules (formula II) to a single alkanol molecule (formula I) is presented by the equation ##STR1##
Alkylene oxide addition reactions are known to produce a product mixture of various alkoxylate molecules having different numbers of alkylene oxide adducts (oxyalkylene adducts), e.g., having different values for the adduct number n in formula III above. The adduct number is a factor which in many respects controls the properties of the alkoxylate molecule, and efforts are made to tailor the average adduct number of a product and/or the distribution of adduct numbers within a product to the product's intended service.
In one respect the present invention is a process for the production of an alkanol alkoxylate product having a narrow-range alkylene oxide adduct distribution. Alkoxylate mixtures in which a relatively large proportion of the alkoxylate molecules have a number (n) of alkylene oxide adducts that is within a relatively narrow range of values have been reported as being preferred for use in certain detergent formulations (Great Britain Pat. No. 1,462,134; Derwent Publications Research Disclosure No. 194,010). Narrow-range alkoxylates are also known to be particularly valuable as chemical intermediates in the synthesis of certain carboxyalkylated alkyl polyethers (U.S. Pat. No. 4,098,818) and of certain alkyl ether sulfates (Great Britain Pat. No. 1,553,561).
More particularly, the present invention provides an improvement upon a process described and claimed in the recently issued U.S. Pat. No. 4,721,816, entitled "Preparation of Nonionic Surfactants". That patent discloses that alkanol alkoxylates characterized by a narrow-range alkylene oxide adduct distribution and by a low content of residual alkanol are prepared in a process which comprises contacting and reacting an alkylene oxide reactant comprising one or more C.sub.2 to C.sub.4 vicinal alkylene oxides with an alkanol reactant comprising one or more C.sub.6 to C.sub.30 alkanols in the presence of a catalytically effective amount of a catalyst prepared by contacting (i) sulfuric acid and (ii) one or more aluminum compounds selected from the group consisting of aluminum alcoholates and aluminum phenolates, the molar ratio of (i) to (ii) being in the range from about 0.1:1 to 2:1.